The present invention relates generally to a method for quantifying plants and, more specifically, to the use of an active light sensor to quantify plants.
It is common knowledge to growers that the amount of plants per area (stand count) is a good indicator of the yield potential and quality of planting in certain crops, especially corn. It is also known there can be a significant drop in yield when a large gap between plants occurs. This can be caused by an unintended planting skip by the seeder or a failure of the seed to germinate and emerge. There is also a drop in yield when seeds are planted too close together due to the competition for resources. Knowing the importance of stand counts, most field corn growers, seed corn growers, researchers, agronomists, and seed companies regularly perform stand counts in their fields. The biggest obstacle to an accurate stand count is the amount of plants in a single field. It is time prohibitive to count all plants in an entire field, so most growers count the number of plants in a 1/1000th of an acre. These counts are used to assume the average stand for the entire field. This could lead to a very inaccurate count and it does not allow the growers to monitor the spatial variation of emergence.
Active light sensors can detect if a plant is present through a change in the reflection of light which is an indication of biomass of a living plant. This process has been indicated in a previous U.S. Pat. No. 5,789,741. In this patent an active light sensor is used to detect the presence of a plant. The goal of the '741 invention is to reduce product application by only applying to plants that are present. Several other patents have at least one part of their claims to be the ability to distinguish between two objects such as the soil and plants. In these claims, the difference is simple definition of a plant or soil reading. This is typically used to determine when to apply or when not to apply a product. Two examples of those claims can be seen in U.S. Pat. No. 7,081,611 and U.S. Pat. No. 5,585,626. What is lacking in this prior art is distinguishing between soil and plants for the purpose of monitoring plant population, plant spacing, economic loss from missing or damaged plants and prescribing a variable application rate that excludes sensor readings from the soil between plants.
The prior art is also lacking in additional descriptions of key features that can improve the knowledge of field conditions. Active light sensors have the ability to distinguish between plants and soil, information which can be used to count the number of plants present in the field. A second feature is the ability to determine the spacing between the plants. A third feature is determining if an area of the field is missing a plant where one should have been or if a plant is severely stunted in growth leading to little to no yield. A fourth feature is using sensors to determine the yield loss and the subsequent economic loss from unproductive plants. It should be noted that all of these features can apply to many other crops, not just corn.
Current active light sensors on the market will sample at a small rate per second when collecting data. Typically sample rates are at 1 Hz to 5 Hz. Rarely do they exceed a 10 Hz sample rate due to the amount of data that will be recorded if one logged all data values. There is a significant flaw in this sampling method as it assumes that all points sampled will be of the best view of the plants being scanned. This is not true especially in early growth row crops such as corn. If a sample is taken at anytime where more soil is scanned than plant, the reflected light of that sample will not accurately reflect the true vigor of the plant nearby. The end result is data that suggests the plant is unhealthy and needs attention. This would result in an inaccurate response such as applying more fertilizer when only a little was needed. This can be corrected by knowing if a plant is present or not at the time of the sample.
The prior art does not address sampling at a high rate and filtering the data though an algorithm to determine when a plant is sampled and when soil is sampled. If the process of filtering the data is done efficiently and accurately, the system can use data when a plant is being directly sampled and all other data sampled can be disregarded.